1. Field of the Invention
The present invention relates to a thermosetting resin composition having superior processability and thermal resistance.
2. Description of the Prior Art
Various kind of thermosetting resins are so far widely used for the production of various insulators, structural materials, adhesives and the like by casting, impregnation, laminating and molding. In recent years, however, the thermosetting resins are required to be more excellent in properties, particularly in thermal resistance because of severe needs for such uses.
In order to meet such requirement, thermosetting polyimide resins have been used. However the processability thereof is not good, so that heating for the processing should be carried out at a high temperature for a long period of time.
While, there are known certain kinds of epoxy resin improved in the thermal resistance, which are good in processability. However, their thermal resistances required to a high degree, such as mechanical and electrical properties at a high temperature and durable heat degradation resistance are not yet satisfactory.
In addition, there are proposed a thermosetting composition comprising a polymaleimide and an polyallylphenol in Published unexamined Japanese Patent Application No. 994/1977, and a thermal resistant resin composition comprising maleimide compounds and polyallylphenol compounds in Published unexamined Japanese Patent Application No. 134099/1978.
However, in these compositions, particularly Novolak type resin-containing composition, there is a defect such that the allyl groups of polyallylphenol readily remain unreacted even after the curing, and the remaining allyl groups have a bad effect on the properties of the cured products. This is probably because the polyallylphenol compounds to be used may be prepared by Claisen rearrangement of polyallylether compounds, so that the allyl group and the hydroxyl group are located each other at the ortho position of the benzene ring.
Under these circumstances, the present inventors have undertaken extensive studies to find a thermosetting resin composition superior in both the thermal resistance and processability, and as a result, found that the object can be accomplished by a resin composition comprising a specified novolak type resin and a maleimide compound.